A winner of the Fields Medal, often called the ‘Nobel Prize of mathematics’, had his prize stolen shortly after receiving it during a ceremony in Rio de Janeiro on Wednesday.

Caucher Birkar, a Kurdish refugee from Iran teaching at Cambridge University, put the gold medal, worth around $4,000, in a briefcase and soon afterwards realised that it had been stolen, according to event organizers.

Security officials at the Riocentro venue, Riocentro, found the empty briefcase in a nearby pavilion. Police reviewed security tapes and identified two potential suspects.

“The International Congress of Mathematicians is profoundly sorry about the disappearance of the briefcase belonging to mathematician Caucher Birkar, which contained his Fields Medal from the ceremony this morning,” organizers said in a note.

It was the first time that the awards, held every four years, were hosted in the southern hemisphere.